如何使用使用基于表单的登录的java web应用程序通过AJAX处理身份验证

I have a java web application running on WebSphere 7. The application uses form authentication method and part of the application accesses some protected resources using ajax requests. However, when the user's session expires, I am getting the login page in place of the content that is supposed to be refreshed by the ajax request. I have a java web application running on WebSph